====== LamaPLC: CJMCU-219/INA-219 breakout board/IC with I²C communication  ======
{{ :sensor:ina219.png?180|CJMCU-219/INA-219 breakout board/IC with I²C communication}}
The **CJMCU-219** is a //breakout board// featuring the **INA219** //IC//, a zero-drift, bidirectional current and power monitor with an [[com:basic_i2c|I²C]] interface.

**Core Technical Specifications**

  * **Voltage Measurement:** Can detect bus voltages from **0V to +26V DC**.
  * **Current Range:** Measures **up to ±3.2A** bidirectionally using its built-in 0.1 ohm shunt resistor.
  * **Supply Voltage:** Operates on **+3.0V to +5.5V**.
  * **Precision:** Features a 12-bit ADC with a maximum error accuracy of 1% over -40°C to +85°C.
  * **Interface:** Uses I²C communication (standard 100kHz or high-speed 400kHz/3.4MHz) with a default address of **0x40**. 

**Key Features**

  * **High-Side Sensing:** Unlike many sensors, it can measure current on the high side (between the power source and the load), thereby avoiding ground-reference issues.
  * **Multi-Function Reporting:** It calculates and reports bus voltage, shunt voltage drop, current, and total power (W) directly.
  * **Programmability:** Supports software-programmable calibration, filtering (averaging up to 128 samples), and conversion times.
  * **Daisy-Chaining:** Supports up to 16 programmable I²C addresses, allowing multiple modules to run on the same bus. 

**Safety & Limitations**

  * **Voltage Limit:** The chip may be damaged if bus voltage exceeds its absolute hardware limit of 26V.
  * **Inductive Loads:** Users should be cautious with large motors, as //"flyback"// voltage spikes can exceed the 26V threshold and destroy the sensor. 

{{page>:tarhal}}

====== CJMCU-219 Pinout ======
{{ :sensor:ina219_1.png?400|CJMCU-219 Pinout}}
**Logic and Power Pins**

These pins connect to your microcontroller (e.g., Arduino or Raspberry Pi) to power the sensor and transmit data. 

  * **VCC:** Supply voltage for the module (**3.0V to 5.5V**).
  * **GND:** Common ground for both power and logic.
  * **SCL:** I²C serial clock line.
  * **SDA:** I²C serial data line.
 
**Measurement (Load) Pins**

These pins are placed in series with the positive side (high-side) of the circuit you want to monitor. 

  * **Vin+:** Connect to the positive terminal of your power source (e.g., battery).
  * **Vin-:** Connect to the positive terminal of your load (the device being powered). 

**I²C addressing Pins (A0 & A1)**

Some versions of the CJMCU-219 include solder pads labeled **A0** and **A1**. By default, these are connected to GND, setting the I2C address to **0x40**. 

Bridging these pads to VCC allows you to set the address to any of 16 values (**0x4F**), enabling multiple sensors on the same I²C bus. 

<color red>Caution: The maximum bus voltage the Vin pins can safely handle is 26V DC.</color>
==== Arduino wiring ====
  * VCC → Arduino 5V (o 3.3V).
  * GND → Arduino GND.
  * SCL → Arduino SCL (A5 on Uno/Nano).
  * SDA → Arduino SDA (A4 on Uno/Nano).
  * Vin+ → Positive side of your power supply.
  * Vin- → Positive side of your load (the device being powered). 

==== Arduino code ====
To begin using the CJMCU-219 with Arduino, the easiest approach is to use the **Adafruit INA219** library.

This example code sets up the sensor and outputs voltage, current, and power readings to the Serial Monitor at **115200 baud**.

A simple example with the Adafruit_INA219 library involves initializing the sensor and repeatedly reading and displaying bus voltage, shunt voltage, load voltage, current, and power. The complete code is available in the provided source document.
<code c>
#include <Wire.h>
#include <Adafruit_INA219.h>

Adafruit_INA219 ina219;

void setup(void) {
  Serial.begin(115200);
  while (!Serial) { delay(1); } // Wait for serial port to connect

  // Initialize the INA219 (default address 0x40)
  if (!ina219.begin()) {
    Serial.println("Failed to find INA219 chip");
    while (1) { delay(10); }
  }

  // Optional: Set calibration for higher precision
  // Default is 32V, 2A. Alternatives:
  // ina219.setCalibration_32V_1A();
  // ina219.setCalibration_16V_400mA();

  Serial.println("Measuring voltage and current with INA219...");
}

void loop(void) {
  float shuntvoltage = 0;
  float busvoltage = 0;
  float current_mA = 0;
  float loadvoltage = 0;
  float power_mW = 0;

  // Read data from sensor
  shuntvoltage = ina219.getShuntVoltage_mV();
  busvoltage = ina219.getBusVoltage_V();
  current_mA = ina219.getCurrent_mA();
  power_mW = ina219.getPower_mW();
  loadvoltage = busvoltage + (shuntvoltage / 1000);

  // Print results
  Serial.print("Bus Voltage:   "); Serial.print(busvoltage); Serial.println(" V");
  Serial.print("Shunt Voltage: "); Serial.print(shuntvoltage); Serial.println(" mV");
  Serial.print("Load Voltage:  "); Serial.print(loadvoltage); Serial.println(" V");
  Serial.print("Current:       "); Serial.print(current_mA); Serial.println(" mA");
  Serial.print("Power:         "); Serial.print(power_mW); Serial.println(" mW");
  Serial.println("");

  delay(2000);
}
</code>
**Key Functions Explained**

  * //begin():// Starts I2C communication. It uses address 0x40 by default.
  * //getBusVoltage_V():// Returns the voltage between GND and the load (V-).
  * //getShuntVoltage_mV():// Returns the voltage drop across the 0.1 ohm resistor.
  * //getCurrent_mA():// Returns the current flowing through the sensor.
  * //getPower_mW():// Calculates power based on the current and bus voltage. 

**Calibration for Accuracy** 

The library includes built-in calibration modes to improve precision for specific ranges: 

  * **Default:** 32V, 2A (Used if no other function is called).
  * **setCalibration_32V_1A():** Increases precision for current measurements up to 1A.
  * **setCalibration_16V_400mA():** Highest precision for low-voltage, low-current projects. 

===== I²C topics on lamaPLC =====
{{topic>i2c}}

\\
\\

{{tag>CJMCU-219 INA-219 INA219 breakout_board i2c communication sensor voltage current arduino code CJMCU}}

This page has been accessed for: Today: {{counter|today}}, Until now: {{counter|total}}